The importance of fibres in achieving impact tolerant composites

The damage tolerance and reliability of two different types of fibre reinforced composite materials are described. In both cases it can be shown that properties necessary for reliable engineering application can be achieved by the incorporation of high strength, high modulus brittle fibres in their microstructures. The brittle fibre - ductile matrix system of boron reinforced aluminium is examined first. It is shown that the ability of this system to dissipate impact energy can exceed that of a monolithic unreinforced titanium alloy. This superiority, however, is extremely test dependent and a method of data presentation is used which clearly elucidates the importance of boron fibre diameter. The second system discussed is graphite fibre reinforced glass and it is shown that, despite the fact that both constituents are quite brittle, a tough material is obtained by this combination.